Globally, a wide range of pockmarks have been identified onshore and offshore. These features can be used as indicators of fluid expulsion through unconsolidated sediments within sedimentary basin-fill. The Great South Basin, New Zealand is one such basin where paleo-pockmarks are observed at around 1,500 m below the seabed. This study aims to describe the characteristics of the paleo-pockmarks in the Great South Basin. Numerous paleo-pockmarks are identified and imaged using three-dimensional seismic reflection data and hosted by fine-grained sediments of the Middle Eocene Laing Formation. The paleo-pockmarks are aligned in a southwest to northeast direction to form a fan-shaped distribution with a high density of around 67 paleo-pockmarks per square kilometer in the centre of the study area. The paleo-pockmarks in this area have a similar shape, varying from sub-rounded to rounded planform shape, but vary in size, ranging from 138 to 481 m diameter, and 15 to 45 ms (TWT) depth. The origin of fluids that contributed to the paleo-pockmark formation is suggested to be biogenic methane based on seismic observations. The basin floor fan deposits beneath the interval hosting the paleo-pockmark might have enhanced fluid migration through permeable layers in this basin-fill. The model can help to explain pockmark formation in deep water sedimentary systems, and may inform future studies of fluid migration and expulsion in sediment sinks.

中文翻译：

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新西兰大南盆地古麻点的地震特征

在全球范围内，陆上和海上已经发现了广泛的麻点。这些特征可用作通过沉积盆地填充物内未固结沉积物排出流体的指标。新西兰的大南盆地就是这样一个盆地，在海床以下约 1,500 m 处观察到古麻点。本研究旨在描述大南盆地古麻点的特征。使用三维地震反射数据识别和成像了许多古麻点，这些麻点由中始新世 Laing 组的细粒沉积物承载。研究区中心古麻点呈西南至东北方向排列，呈扇形分布，密度高，每平方公里约67个古麻点。该地区的古麻点形状相似，从亚圆形到圆形平面形状不等，但大小不同，直径从 138 到 481 m，深度从 15 到 45 毫秒（TWT）。根据地震观测，古麻点形成的流体来源被认为是生物甲烷。古麻坑所在层段下方的盆地底扇沉积物可能增强了流体通过该盆地填充物中的渗透层迁移。该模型可以帮助解释深水沉积系统中的麻点形成，并可能为未来沉积物汇中的流体迁移和排出研究提供信息。根据地震观测，古麻点形成的流体来源被认为是生物甲烷。古麻坑所在层段下方的盆地底扇沉积物可能增强了流体通过该盆地填充物中的渗透层迁移。该模型可以帮助解释深水沉积系统中的麻点形成，并可能为未来沉积物汇中的流体迁移和排出研究提供信息。根据地震观测，古麻点形成的流体来源被认为是生物甲烷。古麻坑所在层段下方的盆地底扇沉积物可能增强了流体通过该盆地填充物中的渗透层迁移。该模型可以帮助解释深水沉积系统中的麻点形成，并可能为未来沉积物汇中的流体迁移和排出研究提供信息。